Fig. 5: Golgotha Cave monitoring data.

a Smoothed monthly meteoric precipitation (P) anomalies (cerulean blue). b Monitored drip rates for speleothem sites GL-S1 (red), GL-S2 (green), GL-S3 (navy blue) and GL-S4 (purple). c Smoothed precipitation-weighted monthly rainfall δ¹⁸O (grey dash) and smoothed dripwater δ¹⁸O for drip sites where speleothems were collected (colours as for drip rates); mean δ¹⁸O values of matrix (orange squares) and fracture flow sites (blue diamonds) in the drip logger array sampled during five field campaigns. Error bars represent ±1σ of measurements from multiple sites. Monthly precipitation anomalies were calculated using the monthly climatological means from 1950 to 2020. An exponentially-weighted moving average (EWMA) was applied to monthly P anomalies with a half-life parameter of 36.6 months; similarly an EWMA was applied to monthly rainfall δ¹⁸O using a 25 month half-life, as well as a lag of 19 months supported by our field studies in refs. ^40,51. Dripwater δ¹⁸O were smoothed with a loess 2nd order filter (span 0.3). Drip rates exhibit a threshold response to higher infiltration indicating the relative influence of fractures on each flowpath⁴⁰. For example, the drip for GL-S4 rapidly increases in response to higher precipitation anomalies during 2013 compared to the much smaller rise in the drip rate for GL-S1, indicating that a larger fracture component is feeding GL-S4. Over the same period, mean drip rate of the logger array increased from 0.16 ± 0.02 to 0.20 ± 0.40 for matrix flow sites and from 2.21 ± 0.40 to 8.32 ± 3.43 for fracture flow sites. The relative contribution of fracture flow to each drip site is inversely related to drip δ¹⁸O values with activation of fractures occurring during periods of higher infiltration associated with lower rainfall δ¹⁸O values.